Art of drying materials



Dec. 8, 1925 G. D. HARRIS ART OF DRYING MATERIALS Filed Feb. 18. 1924 ssheets-snee; 2

Dec/8, 1925. 1,564,566

G. D. HARRIS 1 ART. OF DRYING MATERIALS Filed Feb. is, 1924 6 ssheetssheet I ,4 TroR/VEY.,

Patented Dec. 8, 1925. fr

"UNITED STATES PATENT OFFICE.-

GORDON DON' HARRIS, OE FREEPORT, NEW YORK,` ASSIGNOR TO THE INDUSTRIALDRYER CORPORATION, STANFORD, CONNECTICUT, vA CORPORATION F CON-NECTICUT.

ART OF DRYING MATERIALS.

t j To all 'whom zt may concern.'

Be it known that I, `GronnoN DoN HARRIS,

'l a citizen of the United States, residing at Freeport, county ofNassau, and State of' New York, have invented a certain new and usefulImprovement in the Art lof Drying Materials, of which the following is aspecification. f

This invention pertains to the art of dr ing materials in accordancewith a determined or prescribed formula with respect to the conditionsof temperature and humidit ture and the moisture content of such dryofthe drying atmosphere and also wit 1 reference to the moisture coutentand the character ofthe material under treatment.

' The invention includes both a method and an apparatus, and it is usedfor the treatlnent of a wide variety of materials, including leather,ceramic Ware, and other products the physical characteristics of whichdemand that during the drying period there shall be present in thedrying atmosphere flowing into contact with the material therequiredheat units to eect the exchange of heat in ,theatmosphere for.moisture in the material and that such drying atmosphere shall contain,also, a certain humidity the percentage of which is in a definite ratioto the moisture content of the material under treatment.

ln 'the treatment of a certain class of materials, such as leather, ithas ,been determined by experience and investigation that, to attain therequired results in conditionmg such material, the drying atmosphere'shall be maintained at a constant temperaing atmosphere, shall, also,

be constant, irrespective of a decrease 1n the ratio of moisturediffusion within the material under4 treatment, to the end that the heatcarried 'by the drying atmosphere will be exchanged for moisture in thematerial While the lmmidity pesent in the drying atmosphere will alsocarried into contact with the material with the object rof precludingthat condition of such material known` as case hardemng", wherein a filmon the surface closes the pores against the free "exudation of moisturepresent Within the mass of such material.

Again, in the treatment vof other classes of materials, such as ceramicwares, it has been determined -byinvestgation and expetl'le interior ofmoisture decreases from the material under` treatment, the heat unitsand the percentage of moisture present in the drying atmos- ,phere shallvary as the drying of the material progresses, with the result that theheat i units present in the atmospherewill progressively increase andthe moisture content of the atmosphere will also progressively increase,or vice versa, the atmosphere will carry heat units in decreasingpercentage while the moisture content of such atmosphere will remainconstant, or be increased. As an example, in the condi-tion vof thedrying atmosphere, for evaporating materials such as leather, whereinconstant temperature and constant humidity are desirable, the dryingatmosphere is heated to a temperature of 100 Fahr., and` contains 85humidity, and these conditions of heat and humidity are renderedconstant by boosting the atmosphere and renewing such atmosphere at amore or less frequent interval, determined and controlled by thecondition of the atmosphere itself acting through instrumentalitiesknown to the art, whereby an excess of humidity in the atmosphere setsinto action certain mechanism that auto evaporation progresses, to theend that the evaporation from the material shall be carried on underconditions which preclude fractures in and breaking of the materialitself. Experience in .the treatment of ceramic materials to elimiratemoisture there'- from preparatory to firing or bakin the materials inorder to vitrify the same, s qws 'that a large percentage of breakage 1s1ncurred due to the un ual or ununifqrm evaporation of moisture om areasvarying product under treatl' les there is present in each piece ofmaterial, such as ceramic ware, certain parts of greater cross sectionthan other parts of such materal which are comparatively thin in crosssection, andwhile the dryingof the areas of thin cross section is notdiliicult of accomplishment, the problem is presented of -evapor-atingmoisture from the areas of thicker cross section in a definite relationto the evaporation taking place in areas of thin cross section, becausethe fractures of the material are -occasioned by the une ual contractionand expansion of the ma erial itself in the process of eliminatingmoisture from the areas of thin and thick cross sec-` tions. Accordingto my invention,-vthe drying atmosphere itself is nditioned both asconcerns the heat carrigd thereby, and as to its moisture content, andsuch conditioning of the atmosphere is controllable automatically, tothe end that the heat and the humidity shall vary as the evaporation ofthe materials progresses, such variation including an increase of heatunits and an increase in the moisture content of the drying atmosphere.At the initial stage in evaporating moisture from ceramic ware, thedrying atmosphere is conditioned by heating it to a temperature of 75Fahr. and charging or supplying moisture to-95" humidity, but

as the evaporation of moisture proceeds from the ceramic ware, it isfound that the areas of thin cross section will become dry, orrelativelydry, whereas the areas of greater cross section will stillcontain an appreciable mois ture content which it is essential shall beeliminated during the drying process without resulting in fracture' ofthe ware itself and which elimination of moisture shall be effectedprior to ring or baking-the ware.

- Accordingly, as th dryingprogresses the drying atmosphere isconditioned according to the formula or specification by increasing theheat" units and by increasing the moisture content Npresent in suchatmosphere, to the en dv that the,heat units of the atmosphere will beexchanged for' moisture in the areas of. thicker cross section of theceramic ware, Whereas the humidity of\ the'atmos phere will so act uponthe areas of thin cross section of such ceramic ware as to supplynoisture to such thinner areas from the atmosphere itself, as a resultof which the ceramic ware is itself conditioned by the drying atmosphereto the end that unequal expansion and contraction of the ceramic ware,and the yattendant fracture thereof, is

eliminated or minimized, but on the other hand, the evaporationofmoisture from vsuch ceramic ware proceeds gradually and steadily in allareasthereof, notwithstanding the vvariationin thev cross sectionalareas, and

without entailing the breakage so prevalent in the older methods ofdrying materials ot v Figure 3 is a vertical -mosphere, the latter beinthis character. As inthe example hereinbefore mentioned in connectionwith the evaporation of materials such as leather, the drying atmospherefor treating material such as ceramic ware, is conditioned by heatingand reheating such atmosphere to the required temperature ortemperatures, and by renewing a definite volume of moisture ladenatmosphere with a similar volume of fresh atmospheric air, suchconditions of said atmosphere setting into action the tempera ture andhumidity controls whereby the acts of boosting the atmosphere and ofrenewing the same with fresh atmospheric air are performedautomatically, and in case the moisture. content of the a/cmosphere isor becomes too low to conform to the formula or specifications, certaincontrols act to supply humidity tothe atmosphere by feeding thereto adefinite volume of live steam from an available source of supvconstantlthe humidity of the atmosphere, or

for increasing the moisture content, and provision is made, also, forvincreasing' the moisture content of such atmosphere by feeding moisturethereto, all such controls being effected to conform with more or lessaccuracy tothe prescribed formula or standard, andto attain such endsusually by automatic mechanism.

Other functions and advantages of the invention will appear from thefollowing description taken in connection with the drawings, whereinFigure 1 is a vertical section of a drying apparatus suitable forcarrying into practice my invention, and

Figure 2 is a diagrammatic view illustrating oneform of controls bywhich the atmosregards its temperature and humidity and irrespective ofthe ratio of diffusion of the I water content present in the materialunder treatment. A

sectional elevation illustrating another arrangement of the air intakeand the air outlet with respect to the blower and to other parts of theapparatus.

A is a chamber within which the material to be treated is positioned ina manner to be exposed to the action of a drying atrecirculated by therotative motion of a an or blower B. AsI shown, the chamber is providedwith perforated floor a and a perforated roof a', the saine beingadjacent the bottom and the top, respectively, of the exterior casing soas to produce an intake flue A and an eduction flue A2 which are incommunication with the chamber through the perforations in Isaid. floorg and the roof a', respectively.

V'the intake flue A At one end of the apparatus is a heater chamber Cconnected at the bottom with and at the top with a feeding duct D, andwithin said heater -chamber is asuitable heater or radiator E, the samebeing shown as-a steam coil ,with a header e, to' which is connected asteam .supply pipe F leading from a source of steam supply, see Figure2.

The circulating mechanism B for the drying atmosphere 1s operativelypositioned in the feeding duct D, and said circulating mechanism isdriven by power of any appropriate kind", so as to drive the blower atthe required speed.

" The feeding duct is connected. at ,one end through a port al to theeduction flue A2 of d the material. chamber, whereas the other end ofsaid feeding duct is in free communication with the heater chamber` C.To

this feeding duct is coupled an intake duct G open to the atmosphereVand operable under certain damper controlled conditions for lfeedingfresh `atmospheric air to the feeding duct and thence through the heaterchamber C to the material chamber A.

A discharge duct H is connected tothe feeding duct D, the same being atan appreciable distance from the fresh air intake G and the two ductsbeineIr wholly independent of each other, although both of them are incommunication with the feeding duct. In the fresh air intake ispositioned a valve or damper g, whereas a similar valve or damper k ismounted in the discharge duct H. Said dampers g, la, are'hung. forpivotal movement within the respective ducts G H, and as shown', thedampers are conjointly. operated by a` rod llinked to th'edampers so asto open dampers whereby the fresh air duct G is Vopened and closedconcurrently with the openingand closing of the moisture laden airdischarge duct H., With the dam ers g, ft, in closed positions lwithinthe uets G H. and with the blower in motion, said lblower draws thedrying atmosphere from chamber A through the duct D and blows theatmosphere through chamber C and thence into the chamber A, the effect`offwhich is to recirculate the atmosphere alternately through chambersYA C and thus to reheat and boost the atmosphere by 'contactwith theradiator E. By opening the dampers 'r/ h, in the lues- G H,respectively, and4 an outlet 1s prowith the blower inzmotio'n, videdthrough duct H forl discharging moist hot air Vin a definite volume, andat the same time the'blower draws in a corresponding volume of freshatmospheric (new) 'air to replace the moist air thus discharged from thecirculatory path, which latter includes chambers A C and duct D. The'fresh air thus drawn into the circulatory path byand1 close the ithermometer the blower is mixedfwitli the warm,

moist air and thus the drying atmosphere is conditioned by the admixturetherewith of new air and by boosting the same through the action of theradiator E.

The flow of steam to the radiator is controlled by a valve I, and thisvalve is in 'turn under the control of an automatic temperatureregulatorJ responsiveto the temperature of the drying atmosphere and positionedwithin chamber A, said temperature regulator being of `any charactersuitable for the purpose and adapted to be .set

manually, so that upon Va decrease in thethe drawings there is shown afluidpressure j mechanism which is operatively related not only to thetemperature regulator, but is 'similarly' related to the humiditycontrols, presently referred to. The motive fluid (air in the exampleshown) is accumulated withi in a tank K by theaction of a compressor 7cdriven by a motor le', said compressor having a valved connection 7a2-with said tank, and from this tank leads a main l, from which isbranched a plurality of ipes m, 71,( o. The pipe in. is connected wittemperature regulator J and leads thence through a branch mto automaticvalve I, whereby` the action of sa1d regulator J, responsive v. `to achange in the tem ing atmosphere, contro' elf the ow of steam totheradiator, as the mosphere may demand.

erature of thedry- -the flow'. ofaimo- 'tive iuifd to the valve I vforautomatically said valve inv feeding and shutting An excess.. ofhumidity in-'the .dryingatmosphere, i. e. an increase in the moisturecontent of sa1datmosphere above that conditionl whlh 1t 1s desired toestabl1sh and maintain in said atmosphere, influences -a controlmechanism P which v1s responsive to 'an lncrease or decrease 1n themoisture content ofthe drying atmosphere, and which is positioned withinchamber A so as to be' ex-v posed for Contact with the atmospherecirculating into contact with tlie'material. 'Said humidity controlmechanism P includes a wet bulb thermometer p' and .a dry bulb pf with awell known'provision for manually setting said therm meters in amannertoinsurethe action of Ale control mechanism as a unit when the moisturecontent ofthe drying atmosphere exceeds ther limit of the humiditydesired. Said humidity responsive control mechanism P is operativelyconnected with a damper shifting mechanism herein illustrated in theform oi a pistoucylinder N within which is slidable a spring-actuatedpiston N the -rod of which is connected to a bell crank q linked bya'rod g to another bell crank g2, the latter-being pivoted to thedamper4rod z', see Figure 2. With the humidity control mechanism P co-operatesthe motive fluid 'pipe n: .leading from .the lmain Z, said pipe n havinga branch leading from the thermometers p p to and connected with, thedamper actuating mechanism. The humidity responsive control P ismanually set to become operative when an excess of humidity exists' inthe drying atmosphere above that limit at which it is desired tomaintain said'atmosphere, and when this condition is reached,

the elements p p open the path for the flow 4 of motive fluid throughpipes n n to the pistonmechanism, whereby the dam ers g,

h, are opened automatically for the lower to draw in through the intakeduct G a supply of fresh atmospheric (new) air, and at the same time toexpel through the discharge duct H a corresponding Volume o humid hotair. Provision is thus made for conditioning the drying atmosphere byexpelling a definite volume of humid air and replacing the expelled airwith fresh air, whereupon the control mechanism P is influenced to shutyofthe 'flow of motive fluid to piston cylinder N and the dempers g, h,are closed in the intake and exhaust ducts G H, respectively.

f Provision is made for automatically feeding moisture into. the dryingatmosphere should the humidity all below a determined limit, experiencehaving shown that there are occasions in the service of the machine whenthe drying atmosphere attains a low' humid condition unsuitable for thetreatment of a material or materials possessing certain physicalproperties, as, e. g. in the 'evaporation of moisture from ceramic wareof ununiform cross sectional dimensions and4 in the treatmei t of hidesthe cross sectional thickness of which varies in different areas. v

A steam jet nozzle R is positioned for dischargin live steam into thefeeding duct D for a mixture with the drying atmosphere mi the`dry1ngatmosphere.

mechanism S is a thermometer of a known, type, positioned inchamber Afor exposure yto be recirculated by the blower B, and to this jet nozzleis coupled, a feed pipe r branchedol' the steam main F. The 4iow ofsteam is established by opening an autoy lnatic valve R inth'e pipe 7',and this val/ve i's actuatedautomatically by a control mechanism Sresponsive to a 10W moisture 1content- Said control to Contact withthedrying atmosphere, andr @5 provided `with setting mea-ns operable.manually to render the thermometer responsivey to the moisture contentof the atmospherev4 when it decreases below a desired llmlt.

With this control mechanism Sco-operates the motiveii-uid pipe 0 havinga branch o leading from the control element S to the automatic valvewhereby said valve is actuated by the vmotive lluid supplied by y,

pipe o when the control element S is 1nluenced by low humidity of thedrying atmosphere. A

In operation, the material to be treated 1s placed within the chamber A,steam admitted tothe radiator, valves g, h, closed, and fan Bu set inmotion for circulating air within the closed path afforded by chambersA, C and duct D. The-air is heated to the required temperature byradiator E, and the iiow of air into contact with the material effectsthe exchange of heat for moisture, so that the temperature of theatmosphere will be decreased by such exchange, although the reheating orboostingof such atmosphere during its'repeated circulation compensatesfor the loss of heat units due to such exchange. and humiditycontrolsexposed to the drys ing atmosphere, it follows that the steamsupply is cut oli' from the radiator when the temperature of theatmosphere remains constant, and with the moisture'content of theatmosphere at the desired saturation, the dampers g, l1., are closed,thus effecting the recirculation by the blower of the atmospherewithinthe closed path. Where a con- With the temperatureO stantdetermined humidity and temperature of the drying atmosphere are desiredfor treatment of the material"`within chamber A, say at 100g Fahr. and85 percent humidvity, the thermometer control J and humidity control Pwill influence the radiator E and damper shifting mechanism N N" g g g2,

sol as to supply steam' to the radiator 4 either one-or all of'them,take .place whenever the` .condition ofthe drying atmosphere changes tosuch an extent that the tempera-` ture and humidity of 'such atmosphereare not, in accordance with the formula or specification determined asdesirable for the treatmentl offa particular material. Obviousl ,the yincrease in the moisture contentI of t e atmos here is dueto moistureevaporated ,from tie product,` whereas the temperature changes ared'ueto 'absorption by such atmosphere of the 'moisture which is exchangedfor heat, suchchanges in the condition of' the drying atmosphere taking1n la definite ratio to evaporation, to maintain the desired operating.temperature of the drying atmosphere.

Again, the humidity control P with the damper shifting mechanism act toopen and close the dampers g, h, when the drying atmosphere reaches acertain moisture content, whereby the valves are opened for exhausting adefinite volume of overcharged humid atmosphere, and to renew the atmoshere by the admission of a proper volume'o new air which is mixed withthe moist humid atmosphere remaining in the apparatus, so that thedrying atmosphere is conditioned in conformity with lthe formula orspecica- 'tion determined upon as suitable or most desirable for thetreatment of a particular product. Furthermore, a decrease in thehumidity of the drying atmosphere,as happens in the treatment of certainproducts, although the temperature may remain constant, or even increaseas the evaporation progresses, such decrease affects the low humiditycontrol AS vso as to actuate the valve R' and provide for the flow ofsteam to the nozzleRfin order to supply moisture to the dryingatmosphere until such atmosphere attains the desired moisture content,

whereupon the-control S closes the valve R- and shutso the continuedsupply of steam to the nozzle.` In treating materials, such 'as ceramicware, with or by a drying atmosphere the temperature and humidity of`which will bev'ari'ed as the drying progresses in conformity with adetermined 'formula or f "specification, the drying atmosphere initiallyis, say, at 75 Fahr. and 95 per cent humidity, but atdifferent stages 1nthe rogress of the evaporation of moisture from t e `product, theatmosphereis conditioned to varyl1 the temperature or the humidity,- orbot temperature and humidity are varied inconformity with the formulathi-ou h the action of the controls J, P, S, anti their associateddevices,- either independently or conjointly,

*in a'manner to su ply`steam to the-radia- .torttoo eii the p ampers'for the exit of humid atmos here and, for the in s of new air, and. orthe addition of moisture to 'the drying. atmosphere to-be recirculated-within the-closed' path, whereby the drying yatmosphere is itselfconditioned .both as respects thetemperature and moisture con-v teneither as to excess or decreased humidity, so as to, attain varyingvdegrees in the temperature and humidity of thel atmos, phere, and toutilize suchconditioned atmospherein such manner-as to constantlymaintain a proper condiion ofthe product under-1' going the drying andconditioning'treat--l ment. f

v In the apparatus shown in Figures 1 and p y 2, the air intake G andair outlet H are ositioned atI one side of blower B, i. era ja. cent thesuction sideof said blower. It

may beadvantageous to position the outlet r H adjacent the pressure sideof the blower, and in Figure 3 there is illustrated another `form ofapparatus, wherein the blower B is positioned intermediate the ends offlue D, the outlet H for the dr ing atmosphere is connected with iiue Da jacent the pressure side of the blower, whereas the air inunderstoodthat the purpose is to locate the blower intermediate the air intakeGand the air outlet H.

aving thus fully described the invention, what I claim as new andldesire to secure by Letters Patent is:

1; In the art of drying and conditioning materials, ,the process whichconsists in re@ circulating a drying atmosphere within a determinedcirculatory ath closed against the admission of \outsi e atmosphericair, heating the drying atmosphere during its recirculation,conditioning the drying atmosphere by the admixture of fresh atmosphericair therewith and Vby discharging from the circulatory patha definitevolume of the atmosphere surcharged with moisture, and controlling thereheating and the renewal of such atmosphere, such vcontrol beindepend-'I ent upon and responsive` to a ciange or changes in thecondition of the recirculated atmosphere itself. l

2. In thefart of drying and conditioning materials, the process whichconsists in re` v circulating a drying atmosphere within a definitel athlclosed against the admission of outsi e atmospheric air, repeatedlyheatingl such atmosphere during its recirculation, conditioning therecirculated vatmosphere by discharging from the circulatory path adefinite volume of the atmosphere surcliarged with moisture andreplacing the atmosphere so discharged with fresh atmospheric. air, andcontrolling the reheating and the 'conditioning of the recirculated atmosphere at stagesdependentt upon and responsive'to changes in thetemperature and moisture content'v lof the atmosphere' itself. e

3.- In the l rtfof drying and vconditioning materials, -.t e` processwhich consists in reat stages dependent upon and res onsive to duringits recirculation, periodically con-Y of the atmosphere dependent uponchanges in the moisture content of lthe atmosphere itself. v

5.' In the' art of drying and conditioning materials, the process whichconsists in recirculating a drying atmosphere within a determinedcirculatory ath; periodically reheating the circulate atmosphere,controlling the periodsl of such reheating by a decrease in thetemperature of the atmosphere ditioning the atmosphere during itsrecirculation by dischargin a. definite volume from the circulatory patVand replacing with fresh airfthe volume so discharged, and controllingthe periods of such reconditioning of the atmps here at stages indicatedby the presence o a moisture content in excess of aj determinedpercentage of humidity in suchatmosphere. p

6. In the art of drying and conditioning materials'the cross sectionalareas of AWhich vary in thickness, the process which consists inrecirculating a drying atmosphere characterized -by the presence of adefinite moisture and heat content into contact with said material,exchangingp heat from the drying atmosphere for moisture in the materialat continuous stages in the recirculation of the atmosphere, and atcertain stages in the conditioning of ,said niaterial feedingmoisture tothe areas of thmner cross section and concurrently therewith evaorating. moisture fromkthe areas of tliic er cross section, whereby theconditioning of the material areasvarying in cross sectionwill progressin definite ratio.

7. Iii the art of drying and conditioningl materials the cross sectionalareas of which vary in thickness, the process which consists inrecirculating a drying atmosphere `char.

acterized by a definite irioitiire and heat content intocontact with,said material for exchanging heat for moisture and ultimatelyy attainthe supply 'of moisture to the areas of thinl cross section Whilecontinuing to evaporate moisture from the areas of thicker A crosssection, reheating said atmosphere durji/ng Ythe v.recirculationthereoffto maintain its Maanen temperature constant, conditioning saidatmosphere by discharging a definite volume of humid atmosphere andfeeding th'ereto a like volume of fresh atmospheric air, and controllingthe periods of such reheating and 'such conditioning of the atmosphereat stages which indicate-a change in the temperature and moisturecontentI 'of such vatmosphere. e

8. In the art of drying and lconditioning materials, the process whichconsists in recirculating a drying atmosphere characterized by adefinite heat and moisture content into contact with the material undertreat ment, reheatin said atmosphere during the recirculation t ereof,conditioning the atmosphere during recirculation by replacing a'definite volume of humid atmosphere with a similar vvolume of freshatmospheric air, and controlling such periods of relieating andconditioning of the atmosphere upon a change in the temperature and inthe humidity of such atmosphere indicating a drop below a determinedlimit of heat and moisture content of the atmosphere.

aov

9. In the art of drying and conditioning ized by a determined heat andmoisture conl u tent into contact with the material, conditioning theatmosphere during recirculation by replacing with fresh atmospheric aira definite volume of such atmospheric air containing an excess ofmoisture, reheating the atmospheric air during recirculation, and

feeding steam into the `atmosphere during recirculation to bringthemoisture content to a desired limit 'or limits,

11. In an apparatus for drying and conditioning materials, means forDcirculating a drying atmosphere within a circulatory path ,closed tothe admission of outsidev atmospheric air, means for reheating suchatmosing means, and humidity responsive meansv for controlling meansoperable for ,conditioning the atmosphere, by replacing a'deiiiiteyoluine-o humid atmosphere with a like'volume of freshatmospheric air.

12. -In an apparatus for dryingand conditioningl materials, lmeans for.circulating a drying atmosphere withinla circulatory,

llO

- drying atmosphere said atmosphere,

i y path closed tov the admission of outside at- Amospherio a1r,meansfor reheatmg such atf mosphere, means for conditioning theatmosphere by replacing a definite volume of humid atmosphere with a'similarvolume of fresh atmospheric air, and humidity-responsive'meansexposed to thecir'culating atmosphere and operatively related to saidconditioning means to actuate the latter upon a change in the moisturecontent of the atmosphere.

13. In an apparatus for drying and conditioning materials, means forcirculating a drying atmosphere Within a circulatory path closed to theadmission of outside atmospheric air, means for reheating suchatmosphere,.means including a damper controlled exhaust and a dampercontrolled intake for replacing a definite volume of humid atmospherewith a like volume of fresh atmospheric air, and humidity responsivemeans positioned for contact with the atmosphere and operatively relatedto said exhaust and intake for shifting the dampers automatically uponan increase above a determined 11m1t 1n the moisture content of' saidatmosphere.

14. In an apparatus for drying and conditioning materials, means forcirculating a drying atmosphere Within a circulatory path closed to theadmission of outside air, means for reheating such atmospere, means forfeeding steam t-o the circulatory path for and humidity responsive meansfor controlling the supply of steam 4upon a ldecrease below a determinedlimit in tlle moisture content of the drying atmosi ere.y

p 15. In an apparatus f or drying and conditioning materials, means forcirculating a Within a circulatory path closed to the admission ofoutside atmospheric air, means for reheating such atmosphere,temperature controlled means for feeding energy tioning materials,means' for clrculating a to the reheating means,l means for supplylngsteam tothe circulan drying atmosphere within a circulatory path closedto the admission of outside atmospheric air, means for reheating suchatmosphere, temperature vcontrolled means for feeding energy to therehcating means, humidlty responsiveA means influenced by an excesshumidity in said atmosphere for replacing a definite volume of humidatmos phere with a like volume of fresh atmospheric air, means forfeeding steam to said atmosphere during recirculation thereof, andhumidity responsive means influenced by a decrease below a determinedlimit in the moisture content of the atmosphere vfor actuating the.steam feeding means to supply additional moisture to the atmosphereduring recirculation thereof.

17. In an appara-tus for drying and conditioning materials, means forrecirculating a drying atmosphere Within a`closed circulatory path, adamper-controlled fresh air intake to said path, a damper controlledmoist air outlet connected With said circulatory path, means responsiveto an excess of the moisture content of the drying atmosphere forvopening the dampers in said fresh air intake and in the moist airoutlet for effecting the discharge of a definite volume of moist airfrom the circulatory path and for feeding to said circulatory path asimilar volume of fresh air, means for reheating the air, andtemperature .controlled means responsiveto a drop in temperature of therying atmosphere for feeding energy to the air reheating means.

18. In an apparatus for drying and conditioning materials, means forcirculating a drying atmosphere Within a closed'circulatory path, avalved fresh air inlet to said circulatory path, a valved moist airoutlet from said circulatory path, means responsive to an excess ofhumidity in the drying atmosphere for openingsaid moist air outletandsaid fresh air inlet, means for reheating the drying atmosphere,temperature controlled means for feeding energy to said reheating means,and means responsive to a low humid condition of the drying atmospherefor feeding steam to said atmosphere.

In testimony whereof I have hereto signed my name this 7th day ofFebruary, 1924.

' GORDON DoN HARRIS,

